Micropiles or minipiles are small, multi-tasking grouted piles with steel reinforcements that support high-capacity loads even in difficult or precarious areas. Helitech leverages micropiles in a variety of different projects for cost-effective and durable solutions.
Micropiles (also known as mini-piles or minipiles) are deep-foundation, small-diameter grouted piles typically consisting of a central steel reinforcement member and also come in cased and uncased versions. Their unique and nimble design allows micropiles to carry very high-capacity loads, often at 250 kips and higher depending on project needs.
Structure of a Micropile
Each part of a minipile works together to reinforce the strength of a foundation system. Micropiles come in both cased and uncased varieties, and include the following parts:
- Standard lead section: The lead section enters the ground first, making way for the micropile.
- Extension and lead displacement plates: Separated by the square or round staff extension, both plates types are applied once the micropile is in the soil. The plates are essential to creating room around the shaft to accommodate the entire structure.
- Steel casing or reinforcement rod: These features are a crucial strengthening element that make micropiles able to withstand high-capacity loads.
Applications for Micropiles
Micropiles can be used in a variety of foundation projects. They are particularly useful when projects are in areas with limited access or weak soil. Minipiles have become a preferred method of deep-foundation stabilization thanks to their reliability, versatility, and efficiency. Micropiles are excellent for:
- Stabilizing difficult terrain: Micropiles are typically used in limited-access areas, such as low overhead clearance, and can be accessed through a typical man door. Micropiles are a cost-effective solution in areas with Karst topography and sloping rock. Because of their versatility in terms of foundation type and small or difficult locations, micropiles are an excellent solution for a variety of structural needs.
- Supporting heavy loads: Loads are typically achieved through skin friction between the grout and surrounding soil or rock. In limited situations, loads can be achieved in end-bearing where the piles are terminated in incompetent rock formations.Unlike a drilled pier, micropiles derive a large percentage of their load from the steel reinforcement. This, along with bearing their load through skin friction, makes micropiles excellent for both tension and compression loads. Steel casing can also be added to address lateral loading requirements. Despite their size, micropiles are a trusted and durable solution for high-capacity needs.
- Maintaining restrictive budgets: With a typical drilled pier foundation, significant cost overruns can occur due to extra rock coring. This can happen as the drilled piers are extended along the face of sloping rock, or when voids are encountered in the rock formation. When these empty areas are discovered, additional rock coring, labor, and budget is required.Micropiles reduce this risk as they typically extend down into the rock formation so the load is transferred by way of skin friction and potential voids of the rock are identified early on. This eliminates risk of voids below the bottom of the drilled pier. Foundations that were once unpredictable or of mixed composition can be easily strengthened with the use of micropiles.
Uses for Micropiles
- Deep foundation projects: Micropiles are a convenient option for establishing a deep foundation because they do not require pre-drilling. Establishing a stable, reliable deep foundation is necessary on job sites of high-capacity loads, onsite barriers, or poor soil.
- Foundation rehabilitation and repairs: When existing foundations are compromised, the use of minipiles helps to fortify the foundation’s stability. The structural load is transferred to the micropiles to create a more suitable and stable soil later. Micropiles are a cost-efficient option in comparison to foundation replacement.
- Foundation stabilization of adjacent structures: Minipiles can be used in projects with nearby structures, or for structures sharing adjacent walls that may interfere with the stability of your project.
Job Types, Micropile Installation and Special Considerations
Micropiles can be used in a variety of projects, including fortification or creation of foundations for structures like bridges, towers, and new buildings. The versatility of micropiles has led to their increased popularity, especially in difficult construction projects. In areas of low clearance, restricted access, or weak soil or foundation types, micropiles are an ideal and reliable solution.
Compared to other foundational projects, micropiles are both customizable and cost-efficient while eliminating the need for additional steps for micropile installations. Because minipiles can be installed without pre-drilling, project completion time and budget are not compromised. In addition to their structural perks, micropiles also offer:
- Control of corrosion and general wear and tear caused by soil
- Consistent, reliable results across project and foundation types
- Quick installation with minimal steps
- The elimination of pre-drilling as a required preparation process, cutting down on work time, staff hours, and costs
- Budget-friendly support without compromising quality
- Lasting strength thanks to a steel core combined with skin friction